Electrically-operated drive device and electrically-operated power steering device

ABSTRACT

An electric power steering device includes a motor housing of an electric motor. The motor housing includes an end face part opposite to an output part of a rotating shaft of the electric motor. An electronic control part is arranged at the end face part. A connector assembly is arranged on a side of the electronic control part opposite to a side of the electronic control part that faces the end face part. A metal cover for the electronic control part includes a bottom part and a lateral peripheral part. The bottom part includes: an exposure hole through which an external terminal forming part is exposed to outside; and an annular reinforcing projecting portion formed at an edge of the exposure hole. The lateral peripheral part is angled from the bottom part, and forms an opening through which the lateral peripheral part is fixed to the end face part.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 371 of PCT/JP2019/041457 filed Oct. 23,2019, which is based upon and claims priority to Japanese patentapplication 2018-204592 filed on Oct. 31, 2018, both of which areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The present invention relates generally to an electric drive device andan electric power steering device, and particularly to an electric drivedevice and an electric power steering device in which an electroniccontrol unit is mounted.

BACKGROUND ART

In a general field of industrial machinery, a controlled object of amechanical system is driven by an electric motor. In recent years,employment of an electric drive device of mechatronical integration typehas been started, wherein the electric drive device includes both of anelectric motor and an electronic control unit in a package, and whereinthe electronic control unit includes semiconductor elements and othersfor controlling rotational speed and torque of the electric motor.

As an example of electric drive device of mechatronical integrationtype, an electric power steering device for an automotive vehicleincludes an electric motor, and an electronic control unit (ECU) forcontrolling the electric motor, wherein the electronic control unit isconfigured to sense a direction and a torque of rotation of a steeringshaft rotated by driver's operation of a steering wheel, and drive theelectric motor based on these sensed values, to produce a steeringassist torque to rotate the steering shaft in the direction of rotationof the steering shaft.

A patent document 1 discloses a known conventional electric powersteering device composed of an electric motor section and an electroniccontrol section. In the electric motor section, an electric motor ishoused in a motor housing, wherein the motor housing has a cylindricalpart made of an aluminum alloy or the like. In the electronic controlsection, a control board provided with electrical components is attachedto an end face wall of the motor housing that is opposite to an outputshaft in an axial direction of the motor housing, wherein the end facewall serves as a heat sink.

The board attached to the end face wall is provided with a power supplycircuit part, a power conversion circuit part, and a control circuitpart, wherein the power conversion circuit part includes power switchingelements such as MOSFETs or IGBTs for driving and controlling theelectric motor, and wherein the control circuit part is configured tocontrol the power switching elements. Output terminals of the powerswitching elements and input terminals of the electric motor areconnected electrically via a bus bar.

The electronic control part attached to the end face wall is suppliedwith electric power from a power supply via a connector assembly made ofsynthetic resin, and also supplied with a sensing signal indicatingoperating states and others from sensors and others. The connectorassembly includes an external terminal forming part that is exposed tothe outside through an exposure hole formed in a metal cover, and isconnected to a connector not shown and connected to the power supply(battery) and sensors.

The metal cover is made of metal to have a bottomed tubular shape withone end open, and includes a bottom side formed with the exposure holethrough which the external terminal forming part is exposed, andincludes an open side fixed to the end face wall of the motor housing byan adhesive or bolts.

Other known examples of electric drive device where an electroniccontrol device is integrally provided include an electric brake device,and an electric hydraulic pressure control device for control of varioushydraulic pressures. The following describes an electric power steeringdevice as a representative example.

PRIOR ART DOCUMENT(S) Patent Document(s)

-   Patent Document 1: JP 2017-216838 A

SUMMARY OF INVENTION Problem(s) to be Solved by the Invention

In the electric power steering device described in patent document 1(particularly, see FIG. 3), the external terminal forming part of theconnector assembly is exposed to the outside through the exposure holeformed in the bottom part of the metal cover. Specifically, as shown inFIGS. 14 and 15 attached hereto, in a metal cover 60, a bottom part 62is formed at one end of a lateral peripheral part 61 with an exposurehole 63 through which an external terminal forming part of a connectorassembly is exposed to the outside.

Exposure hole 63 is formed by punching the bottom part 62, wherein aperipheral edge portion 63C of exposure hole 63 is formed in a planewhere bottom part 62 is formed. Furthermore, an opening 64 is formed onthe opposite side of bottom part 62, is fixed to the end face wall ofthe motor housing.

For cost reduction and weight reduction, it is required to reduce theplate thickness of metal cover 60. However, metal cover 60 is oftensubject to an external force during a process of assembling the metalcover 60 and during a process of use. Therefore, if the plate thicknessof metal cover 60 is small, peripheral edge portion 63C of exposure hole63 and its surroundings are likely to be deformed, and metal cover 60may be further deformed entirely. Such deformation may disable afunction of liquid tightness between exposure hole 63 of metal cover 60and the connector assembly, or a function of liquid tightness betweenopening 64 of metal cover 60 and the end face wall of the motor housing.

In view of the foregoing, there is a demand for an electric drive deviceand an electric power steering device with which those problems aresolved.

It is an object of the present invention to provide a novel electricdrive device and a novel electric power steering device in whichthickness of a metal cover is reduced, and mechanical strength ofsurroundings of an exposure hole formed in a bottom part of the metalcover is enhanced to suppress deformation of the metal cover.

Means for Solving the Problem(s)

According to the present invention, it includes: a motor housingstructured to house an electric motor, wherein the motor housingincludes an end face part opposite to an output part of a rotating shaftof the electric motor, and wherein the electric motor is structured todrive a controlled object of a mechanical system; an electronic controlpart arranged at the end face part of the motor housing; a connectorassembly arranged on a side of the electronic control part opposite to aside of the electronic control part that faces the end face part of themotor housing; and a metal cover structured to cover the electroniccontrol part from outside, wherein the metal cover includes: a bottompart including: an exposure hole through which an external terminalforming part is exposed to outside; and an annular reinforcingprojecting portion formed at an edge of the exposure hole; and a lateralperipheral part angled from the bottom part, and forming an openingthrough which the lateral peripheral part is fixed to the end face partof the motor housing.

Effect(s) of the Invention

According to the present invention, the feature that the annularreinforcing projecting portion is formed at the edge of the exposurehole formed in the bottom part of the metal cover, serves to enhance themechanical strength of the surrounding region of the exposure hole, andthereby suppress the deformation of the metal cover.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a whole perspective view of a steering device as an example ofdevice to which the present invention is applied.

FIG. 2 is a whole perspective view of an electric power steering deviceaccording to an embodiment of the present invention.

FIG. 3 is an exploded perspective view of the electric power steeringdevice shown in FIG. 2.

FIG. 4 is a perspective view of a motor housing shown in

FIG. 3.

FIG. 5 is a cutaway view of the motor housing shown in FIG. 4, where themotor housing is cut by a plane containing a central axis of the motorhousing.

FIG. 6 is a perspective view of the motor housing shown in FIG. 4 wherea power conversion circuit part is mounted and fixed to the motorhousing.

FIG. 7 is a perspective view of the motor housing shown in FIG. 6 wherea power supply circuit part is mounted and fixed to the motor housing.

FIG. 8 is a perspective view of the motor housing shown in FIG. 7 wherea control circuit part is mounted and fixed to the motor housing.

FIG. 9 is a perspective view of the motor housing shown in FIG. 8 wherea connector assembly is mounted and fixed to the motor housing.

FIG. 10 is an enlarged sectional view of an electronic control sectionand its surroundings.

FIG. 11 is sectional view of a metal cover according to the embodimentof the present invention.

FIG. 12 is a perspective view of the metal cover shown in FIG. 11 fromdiagonally above.

FIG. 13 is an enlarged sectional view of the electronic control sectionand its surroundings when the metal cover according to the embodiment ofthe present invention is attached.

FIG. 14 is a sectional view of a metal cover employed by a conventionalelectric power steering device.

FIG. 15 is a perspective view of the metal cover shown in FIG. 14 fromdiagonally above.

MODE(S) FOR CARRYING OUT INVENTION

The following details an embodiment of the present invention withreference to the drawings. However, the present invention is not limitedto the embodiment, but includes various modifications and applicationsbelonging to technical conception of the present invention.

The following briefly describes configuration of a steering device as anexample of device to which the present invention is applied, withreference to FIG. 1, prior to description of the embodiment of thepresent invention.

First, the following describes a steering device for steering frontwheels of an automotive vehicle. Steering device 1 is configured asshown in FIG. 1. A steering shaft 2 is connected to a steering wheel notshown, and includes a lower end formed with a pinion not shown, whereinthe pinion is in mesh with a rack not shown, wherein the rack extends ina vehicle body lateral direction. The rack includes ends linked torespective tie rods 3 for steering the front wheels leftward andrightward, and is housed by a rack housing 4. A rubber boot 5 isprovided between rack housing 4 and each tie rod 3.

An electric power steering device 6 is provided for producing an assisttorque while the steering wheel is being turned. Specifically, electricpower steering device 6 includes a torque sensor 7, an electric motorsection 8, and an electronic control section or unit (ECU) 9, whereintorque sensor 7 is structured to sense a direction of rotation ofsteering shaft 2, and a rotating torque applied to steering shaft 2,wherein electric motor section 8 is structured to apply a steeringassist force to the rack via a gear 10 depending on a sensed value fromtorque sensor 7, and wherein electronic control section 9 is configuredto control an electric motor arranged in electric motor section 8.

Electric motor section 8 of electric power steering device 6 isconnected to gear 10 by screws not shown at three spots of an outerperipheral part of an output shaft side of electric motor section 8.Electronic control section 9 is arranged at a side of electric motorsection 8 opposite to an output shaft of electric motor section 8.

Electric power steering device 6 operates as follows. As the steeringwheel is turned to rotate steering shaft 2 in one direction, torquesensor 7 then senses the direction of rotation of steering shaft 2, andthe rotating torque applied to steering shaft 2. A control circuit partcalculates a quantity of operation of the electric motor, based on asensed value from torque sensor 7.

Power switching elements of a power conversion circuit part arecontrolled to drive the electric motor based on the calculated quantityof operation, so that the output shaft of the electric motor is rotatedto drive the steering shaft 2 in the same direction as the direction ofoperation of the steering wheel. The rotation of the output shaft of theelectric motor is transferred to the rack via the pinion and gear 10,thereby steering the automotive vehicle. Further description is omittedbecause its configuration and operation are well known.

As described above, in the electric power steering device as configuredin patent document 1, the external terminal forming part of theconnector assembly is exposed through exposure hole 63 formed in bottompart 62 of metal cover 60, as shown in FIGS. 14 and 15. Exposure hole 63is formed by punching the bottom part 62, wherein peripheral edgeportion 63C of exposure hole 63 is formed in the plane where bottom part62 is formed. For cost reduction and weight reduction, it is required toreduce the plate thickness of metal cover 60. However, if the platethickness of metal cover 60 is small, peripheral edge portion 63C ofexposure hole 63 and its surroundings are likely to be deformed, andmetal cover 60 may be further deformed entirely.

In view of the foregoing background, according to the presentembodiment, an electric power steering device is proposed which isconfigured as follows.

According to the present embodiment: an electric power steering deviceincludes: a motor housing including an end face part opposite to anoutput part of a rotating shaft of an electric motor; an electroniccontrol part arranged at the end face part of the motor housing; aconnector assembly arranged on a side of the electronic control partopposite to a side of the electronic control part that faces the endface part of the motor housing; an annular seal accommodating portionformed around an external terminal forming part of the connectorassembly, and filled with a liquid sealing agent; and a metal coverstructured to cover the electronic control part from outside, whereinthe metal cover includes: a bottom part including: an exposure holethrough which the external terminal forming part is exposed to outside;and an annular reinforcing projecting portion formed at an edge of theexposure hole, and accommodated in the annular seal accommodatingportion; and a lateral peripheral part angled from the bottom part, andforming an opening through which the lateral peripheral part is fixed tothe end face part of the motor housing.

According to the foregoing, the feature that the annular reinforcingprojecting portion is formed at the edge of the exposure hole formed inthe bottom part of the metal cover, serves to enhance the mechanicalstrength of the surrounding region of the exposure hole, and therebysuppress the deformation of the metal cover. Furthermore, the liquidsealing agent filled between the annular reinforcing projecting portionand the annular seal accommodating portion ensures liquid tightness.

The following details specific configuration of the electric powersteering device according to the embodiment of the present inventionwith reference to FIGS. 2 to 13.

FIG. 2 shows whole configuration of the electric power steering deviceaccording to the present embodiment. FIG. 3 shows components of theelectric power steering device shown in FIG. 2 in disassembled state asviewed diagonally. FIGS. 4 to 9 show states of assembling when thecomponents are assembled in an assembling order.

FIG. 10 is a sectional view of the electronic control section of theelectric power steering device. FIG. 11 is a sectional view of the metalcover. FIG. 12 shows the metal cover as viewed diagonally from above.FIG. 13 is a sectional view of the electronic control section of theelectric power steering device when the metal cover is attached. Thefollowing description refers to these drawings as appropriate.

As shown in FIG. 2, the electric power steering device includes electricmotor section 8 and electronic control section 9. Electric motor section8 includes a motor housing 11 and an electric motor not shown. Motorhousing 11 includes a cylindrical part made of an aluminum-based metalsuch as aluminum or an aluminum alloy. The electric motor is housed inmotor housing 11. Electronic control section 9 includes a metal cover12, and an electronic control assembly not shown housed in metal cover12. Metal cover 12 is made of an aluminum-based metal such as aluminumor an aluminum alloy, or an iron-based metal, and is arranged at a sideof motor housing 11 opposite to the output shaft in the axial direction.

Motor housing 11 and metal cover 12 are fixed to each other by swagingin their fixing regions each extending circumferentially in theperiphery of the end face part facing each other. Metal cover 12includes an accommodation space inside thereof, which accommodates theelectronic control assembly. The electronic control assembly includes apower supply circuit part for supplying electric power as required, anda power conversion circuit part having power switching elements such asMOSFETs or IGBTs for driving and controlling the electric motor ofelectric motor section 8, and a control circuit part for controlling thepower switching elements. Output terminals of the power switchingelements and input terminals of a coil of the electric motor areconnected electrically via a bus bar.

At an end face of metal cover 12 opposite to motor housing 11, a part ofa connector assembly 13 is exposed through an exposure hole 42 formed inmetal cover 12. Connector assembly 13 is fixed by screws to fixing partsof motor housing 11. The part of connector assembly 13 includes anexternal terminal forming part 13A for power supply, an externalterminal forming part 13B for sensors, and an external terminal formingpart 13C for sending a state of control to external devices.

The electronic control assembly housed in metal cover 12 is suppliedwith electric power from a power supply via the external terminalforming part 13A made of synthetic resin, and is supplied with sensingsignals indicative of operating states from sensors and others via theexternal terminal forming part 13B, and sends a present control state ofthe electric power steering device via the external terminal formingpart 13C.

FIG. 3 shows electric power steering device 6 in an exploded perspectiveview. Inside of motor housing 11, a side yoke not shown is fitted,wherein the side yoke has an annular shape and is made of iron. Theelectric motor not shown is mounted inside of the side yoke. Theelectric motor includes an output part 14 structured to apply a steeringassist force to the rack via the gear. Description of specificconfiguration of the electric motor is omitted because it is well known.

Motor housing 11 is made of an aluminum alloy, thereby serving as a heatsink member for dissipating heat to outside atmosphere, wherein the heatis generated by the electric motor, the power conversion circuit partand the power supply circuit part described below. The electric motorand motor housing 11 form the electric motor section 8.

Electronic control part EC is attached to an end face part 15 of motorhousing 11 opposite to the output part 14 of the electric motor section8. Electronic control part EC is composed of power conversion circuitpart 16, power supply circuit part 17, control circuit part 18, andconnector assembly 13. The end face part 15 of motor housing 11 isformed integrally with motor housing 11, but may be formed separatelyfrom motor housing 11 and screwed or welded to motor housing 11.

Power conversion circuit part 16, power supply circuit part 17, andcontrol circuit part 18 are configured to be redundant and form a mainelectronic control system and an auxiliary electronic control system.Normally, the main electronic control system is employed to drive andcontrol the electric motor, and when an abnormality or failure occurs inthe main electronic control system, the control is switched from themain electronic control system to the auxiliary electronic controlsystem so that the auxiliary electronic control system drives andcontrols the electric motor. Accordingly, as detailed below, heat of themain electronic control system is normally transferred to motor housing11. When the main electronic control system is failed or abnormal,operation of the main electronic control system is stopped and theauxiliary electronic control system is activated so that heat of theauxiliary electronic control system is transferred to motor housing 11.

However, although not adopted by the present embodiment, there is analternative configuration that both of the main and auxiliary electroniccontrol systems are simultaneously employed to form a normal electroniccontrol system, and when one of the main and auxiliary electroniccontrol systems is failed or abnormal, only the other electronic controlsystem is employed to drive and control the electric motor with half offull performance. This ensures a power steering function, although theperformance of the electric motor is only half. Accordingly, the heat ofthe main electronic control system and the auxiliary electronic controlsystem is normally transferred to motor housing 11.

Power conversion circuit part 16, power supply circuit part 17, controlcircuit part 18, and connector assembly 13, which form the electroniccontrol part EC, are arranged in this order away from end face part 15of motor housing 11. Control circuit part 18 is configured to generatecontrol signals for driving the switching elements of power conversioncircuit part 16, and includes a microcomputer and a peripheral circuit.

Power supply circuit part 17 is configured to supply electric power todrive the control circuit part 18, and supply electric power to powerconversion circuit part 16, and includes capacitors, coils, switchingelements, and others. Power conversion circuit part 16 is configured toregulate electric power flowing through the coil of the electric motor,and includes switching elements and others forming three-phase upper andlower arms.

In electronic control part EC, power conversion circuit part 16 andpower supply circuit part 17 generate more quantities of heat thanothers. The generated heat of power conversion circuit part 16 and powersupply circuit part 17 is dissipated via motor housing 11 made of thealuminum alloy. This configuration is detailed below with reference toFIGS. 4 to 9.

Connector assembly 13, which is made of synthetic resin, is arrangedbetween control circuit part 18 and metal cover 12, and is connected toa vehicle battery (power supply) and external control devices not shown.Connector assembly 13 is also connected to power conversion circuit part16, power supply circuit part 17, and control circuit part 18.

Metal cover 12 functions to house and seal liquid-tightly the powerconversion circuit part 16, power supply circuit part 17, and controlcircuit part 18. In the present embodiment, metal cover 12 is fixed tomotor housing 11 by swaging.

Metal cover 12 includes a lateral peripheral part 43, and a bottom part44 formed by bending from one end of lateral peripheral part 43. Bottompart 44 is formed with exposure hole 42 through which external terminalforming parts 13A, 13B, 13C of connector assembly 13 are exposed to theoutside. Metal cover 12 includes an open end 37 opposite to bottom part44, wherein open end 37 is engaged with end face part 15 of motorhousing 11.

The following describes configuration of the components and a process ofassembling the components with reference to FIGS. 4 to 9. FIG. 4 showsan exterior view of motor housing 11, and FIG. 5 shows its axialsectional view.

As shown in FIGS. 4 and 5, motor housing 11 is cylindrically shaped andincludes a lateral peripheral part 11A, end face part 15, and a cover19. The end face part 15 closes a first end of lateral peripheral part11A, whereas the cover 19 closes a second end of lateral peripheral part11A. In the present embodiment, lateral peripheral part 11A and end facepart 15 are formed integrally such that motor housing 11 has acylindrical shape having a bottom. The cover 19 serves a coveringfunction to close the second end of lateral peripheral part 11A afterthe electric motor is mounted inside the lateral peripheral part 11A.

The peripheral surface of end face part 15 is formed with an annularstep portion 35 whose diameter is reduced inward in the radialdirection, wherein open end 37 of metal cover 12 shown in FIG. 9 isengaged with step portion 35. The fixation between the side wall of endface part 15 and open end 37 of the metal cover 12 is implemented byso-called swaging fixation.

As shown in FIG. 5, a stator 21 is fitted inside the lateral peripheralpart 11A of motor housing 11, wherein stator 21 is formed by winding thecoil 20 around an iron core. A rotor 22 is rotatably mounted inside thestator 21, wherein a permanent magnet is embedded in rotor 22. Arotating shaft 23 is fixed to rotor 22. One end of rotating shaft 23forms the output part 14, whereas the other end of rotating shaft 23forms a rotation-sensing target part 24 serving as a target for sensingthe rotational phase and speed of rotating shaft 23.

Rotation-sensing target part 24 is provided with the permanent magnet,extending through a through hole 25 formed in end face part 15, andprojecting to the outside. The rotational phase and speed of rotatingshaft 23 is sensed by a magnetic sensor such as a GMR element or thelike not shown.

Referring back to FIG. 4, the surface of end face part 15 opposite tothe output part 14 of rotating shaft 23 is formed with a heatdissipation region 15A for power conversion circuit part 16 (see FIG. 3)and a heat dissipation region 15B for power supply circuit part 17 (seeFIG. 3). Four corners of end face part 15 are each formed integrallywith a board-fixing projecting part 26 extending perpendicularly fromend face part 15. Each board-fixing projecting part 26 is formed with ascrew hole 26S inside. Board-fixing projecting parts 26 are structuredto fix a board of control circuit part 18 described below and connectorassembly 13. Each board-fixing projecting part 26 projecting from powerconversion heat dissipation region 15A described below is formed with aboard-receiving part 27 having the same height as power supply heatdissipation region 15B described below in the axial direction. Eachboard-receiving part 27 is structured to mount and fix a glass epoxyboard 31 of power supply circuit part 17 described below.

The flat area forming the end face part 15 and extending in the radialdirection and perpendicular to rotating shaft 23 is divided into tworegions, namely, power conversion heat dissipation region 15A and powersupply heat dissipation region 15B. Power conversion circuit part 16,which is composed of switching elements such as MOSFETs, is attached topower conversion heat dissipation region 15A. Power supply circuit part17 is attached to power supply heat dissipation region 15B. In thepresent embodiment, the area of power conversion heat dissipation region15A is set larger than that of power supply heat dissipation region 15B.This serves to ensure more space for mounting the power conversioncircuit part 16, because the redundant system is employed.

A step is provided between power conversion heat dissipation region 15Aand power supply heat dissipation region 15B such that power conversionheat dissipation region 15A and power supply heat dissipation region 15Bhave different heights in the axial direction (the direction in whichrotating shaft 23 extends). Namely, power supply heat dissipation region15B is formed with an outward step away with respect to power conversionheat dissipation region 15A in the axial direction of rotating shaft 23of the electric motor. This step is set to have a height enough toprevent interference between power conversion circuit part 16 and powersupply circuit part 17 when power supply circuit part 17 is assembledafter power conversion circuit part 16 is assembled.

Power conversion heat dissipation region 15A is formed with three heatdissipation projecting parts 28. Heat dissipation projecting parts 28are configured to mount power conversion circuit part 16 thereon,wherein power conversion circuit part 16 is configured to be redundantas described below. Each heat dissipation projecting part 28 projectsaway from the electric motor in the direction of rotating shaft 23 ofthe electric motor.

Power supply heat dissipation region 15B is generally flat and isconfigured to mount power supply circuit part 17 thereon, where powersupply circuit part 17 is described below. Accordingly, each heatdissipation projecting part 28 serves as a heat dissipation portion totransfer heat from power conversion circuit part 16 to end face part 15,whereas power supply heat dissipation region 15B serves as a heatdissipation portion to transfer heat from power supply circuit part 17to end face part 15.

Each heat dissipation projecting part 28 may be omitted so that powerconversion heat dissipation region 15A serves as a heat dissipationportion to transfer heat from power conversion circuit part 16 to endface part 15. However, in the present embodiment, a metal board of powerconversion circuit part 16 is securely fixed to heat dissipationprojecting part 28 by friction stir welding.

At end face part 15 of motor housing 11 according to the presentembodiment described above, the axial size can be made compact becausethere is no heat sink member. Moreover, since motor housing 11 has asufficient thermal capacity, the heat generated in power supply circuitpart 17 and power conversion circuit part 16 can be dissipated to theoutside effectively.

FIG. 6 shows a state where power conversion circuit part 16 is placed onheat dissipation projecting parts 28 (see FIG. 4). As shown in FIG. 6,power conversion circuit part 16, which is configured to be redundant,is placed on heat dissipation projecting parts 28 (see FIG. 4) formed inpower conversion heat dissipation region 15A. The switching elementsconstituting the power conversion circuit part 16 are mounted on themetal board which is made of an aluminum-based metal in this example,promoting heat dissipation. The metal board is welded to heatdissipation projecting part 28 by friction stir welding.

The metal board may be replaced with a glass epoxy board. In this case,heat dissipation can be enhanced by setting the thickness of the glassepoxy board as thin as possible.

In this way, the metal board is securely fixed to heat dissipationprojecting part 28 (see FIG. 4), to allow generated heat of theswitching elements to be transferred to heat dissipation projecting part28 (see FIG. 4) effectively. The heat transferred to heat dissipationprojecting part 28 (see FIG. 4) is dissipated to power conversion heatdissipation region 15A, and then to lateral peripheral part 11A of motorhousing 11, and finally to the outside. As described above, powerconversion circuit part 16 is prevented from interfering with powersupply circuit part 17 described below, because the height of powerconversion circuit part 16 is shorter than that of power supply heatdissipation region 15B in the axial direction.

As described above, power conversion circuit part 16 is placed on heatdissipation projecting part 28 formed in the power conversion heatdissipation region 15A. Therefore, the heat generated by the switchingelements of power conversion circuit part 16 can be efficientlytransferred to heat dissipation projecting part 28. Furthermore, theheat transferred to heat dissipation projecting part 28 is dissipated topower conversion heat dissipation region 15A, and transferred to lateralperipheral part 11A of motor housing 11, and dissipated to the outside.

FIG. 7 shows a state where power supply circuit part 17 is placed overpower conversion circuit part 16. As shown in FIG. 7, power supply heatdissipation region 15B is covered by power supply circuit part 17.Capacitors 29 and coils 30 of power supply circuit part 17 are placed onglass epoxy board 31. Power supply circuit part 17 is also configured tobe redundant and include power supply circuits each of which is composedof capacitors 29 and coil 30 and arranged symmetrically with each otheras shown in FIG. 7. Electric elements such as capacitors other than theswitching elements of power conversion circuit part 16 are mounted onglass epoxy board 31.

The surface of glass epoxy board 31 facing the power supply heatdissipation region 15B (see FIG. 6) is fixed to end face part 15, incontact with power supply heat dissipation region 15B. As shown in FIG.7, this fixing is implemented by putting a fixing screw not shown into ascrew hole 27S formed in each board-receiving part 27 of board-fixingprojecting part 26, and also putting a fixing screw not shown into ascrew hole formed in power supply heat dissipation region 15B (see FIG.6).

The configuration that power supply circuit part 17 is based on glassepoxy board 31 allows the components of power supply circuit part 17 tobe mounted on both sides of the power supply circuit part 17. Thesurface of glass epoxy board 31 facing the power supply heat dissipationregion 15B (see FIG. 6) is provided with a rotational phase and speedsensing part composed of the GMR element and a sensing circuit notshown. This sensor is configured to sense the rotational phase and speedof rotating shaft 23 (see FIG. 5) in cooperation with rotation-sensingtarget part 24 (see FIG. 5) that is provided at rotating shaft 23.

The configuration that glass epoxy board 31 is fixed to power supplyheat dissipation region 15B (see FIG. 6), in contact with power supplyheat dissipation region 15B as described above, allows the generatedheat of power supply circuit part 17 to be transferred to power supplyheat dissipation region 15B effectively. The heat transferred to powersupply heat dissipation region 15B (see FIG. 6) is transferred andspread into lateral peripheral part 11A of motor housing 11, and thendissipated to the outside. In order to enhance the thermal conductivity,an adhesive agent or dissipation grease or dissipation sheet having ahigh thermal conductivity may be disposed between glass epoxy board 31and power supply heat dissipation region 15B (see FIG. 6).

As described above, power supply circuit part 17 is placed on powersupply heat dissipation region 15B. The surface of glass epoxy board 31facing the power supply heat dissipation region 15B, on which thecircuit elements of power supply circuit part 17 are mounted, is fixedto end face part 15, in contact with power supply heat dissipationregion 15B. Therefore, the heat generated in power supply circuit part17 can be effectively transferred to power supply heat dissipationregion 15B. The heat transferred to power supply heat dissipation region15B is transferred and spread into lateral peripheral part 11A of motorhousing 11, and dissipated to the outside.

FIG. 8 shows a state where control circuit part 18 is placed over thepower supply circuit part 17. As shown in FIG. 8, control circuit part18 is arranged over power supply circuit part 17. Microcomputers 32 andperipheral circuits 33 constituting the control circuit part 18 areplaced on a glass epoxy board 34. Control circuit part 18 is alsoconfigured to be redundant and include control circuits each of which iscomposed of microcomputer 32 and peripheral circuits 33 and arrangedsymmetrically with each other as shown in FIG. 8. Microcomputers 32 andperipheral circuits 33 may be placed on the surface of glass epoxy board34 facing the power supply circuit part 17.

As shown in FIG. 8, glass epoxy board 34 is fixed by fixing screws notshown through the screw holes formed in the top portions of board-fixingprojecting parts 26 (see FIG. 7), wherein glass epoxy board 34 issandwiched between board-fixing projecting parts 26 and connectorassembly 13. The space between glass epoxy board 31 of power supplycircuit part 17 (see FIG. 7) and glass epoxy board 34 of control circuitpart 18 is used for arrangement of capacitors 29 and coils 30 of powersupply circuit part 17 shown in FIG. 7.

Next, FIG. 9 shows a state in which connector assembly 13 is placed fromabove the control circuit part 18. As shown in FIG. 9, connectorassembly 13 is placed over the control circuit part 18. Then, connectorassembly 13 is fixed by putting fixing screws 36 into the screw holeseach formed in the top of board-fixing projecting part 26, sandwichingthe control circuit part 18. In this state, as shown in FIG. 3,connector assembly 13 is electrically connected to power conversioncircuit part 16, power supply circuit part 17, and control circuit part18.

Connector assembly 13 is formed with an annular seal accommodatingportion 45 around external terminal forming parts 13A, 13B, 13C, whereinannular seal accommodating portion 45 is recess-shaped in its axialsectional view. Annular seal accommodating portion 45 is filled with aliquid sealing agent, where an annular reinforcing projecting portion 46is formed at exposure hole 42 of metal cover 12 as described below andaccommodated in annular seal accommodating portion 45. Accordingly,annular seal accommodating portion 45, the liquid sealing agent, andannular reinforcing projecting portion 46 ensures liquid tightnessbetween metal cover 12 and connector assembly 13.

Furthermore, open end 37 of metal cover 12 is engaged with step portion35 of motor housing 11, and is fixed by swaging to motor housing 11 inthe fixing region extending circumferentially. As described above, theannular step portion 35 of the motor housing, which is formed in theperipheral surface of end face part 15, and the open end 37 of metalcover 12 are engaged with each other by so-called spigot engagement orspigot fitting.

FIG. 10 shows an enlarged sectional view of the electronic controlsection and its surroundings before metal cover 12 is attached.

At end face part 15 of motor housing 11, power conversion circuit part16, power supply circuit part 17, and control circuit part 18, whichconstitute the electronic control part, are layered with each other inthis order away from end face part 15. Connector assembly 13 is arrangedon the side of the control circuit part 18 opposite to the side facingthe power supply circuit part 17. However, the order of arrangement ofpower conversion circuit part 16, power supply circuit part 17, andcontrol circuit part 18 may be arbitrarily selected, if the electroniccontrol part is arranged between connector assembly 13 and end face part15.

A plurality of swaging fixation portions 38 are formed in the sidesurface of step portion 35 of end face part to which opening end 37 ofmetal cover 12 is fixed. Swaging fixation portion 38 includes a swagingrecess 40 that is a swaging groove or recess formed in a fixation wall39 extending in the axial direction from the annular step portion 35toward connector assembly 13, wherein step portion 35 is formed in endface part 15 of motor housing 11. Metal cover 12 is fixed by swaging thewall of metal cover 12 into swaging recess 40 with a pressing tool forpressing and plastically deforming the wall of metal cover 12.

Furthermore, the opening end 37 of metal cover 12, and the wall surfaceextending from the annular step portion 35 to fixation wall 39 form anannular space G, which is filled with a liquid sealing agent 41 forliquid tightness without any gap. This forms a seal region for liquidtightness between the end face part 15 and the open end 37 of the metalcover 12, and prevents entrance of moisture and others by this sealregion. This serves to prevent entrance of moisture and others intoswaging fixation portion 38, and thereby suppress corrosion of swagingfixation portion 38, and enhance the mechanical reliability. Thisfurther serves to prevent entrance of moisture and others intoelectronic control section 9, and thereby enhance the electricalreliability as well.

In the present embodiment, swaging recesses 40 each having apredetermined length are arranged at places as required (three places).The wall of metal cover 12 pressed in each swaging recess 40 serves tosuppress movement of metal cover 12 in the rotational direction and inthe axial direction of rotating shaft 23 with respect to motor housing11.

In the region of connector assembly 13 surrounding the external terminalforming parts 13A, 13B, 13C, annular seal accommodating portion 45 isformed continuously. Annular seal accommodating portion 45 is formed ina groove shape in the surface 47 facing the bottom part 44 in a statewhere connector assembly 13 faces bottom part 44 of metal cover 12. Thecross section of the groove may have a rectangular shape, a semicircularshape, or an arc shape.

Annular seal accommodating portion 45 is an annular groove having anopening facing away from the end face part 15 of motor housing 11 in theaxial direction of rotating shaft 23. Therefore, the annular groove isformed along the axis of rotating shaft 23.

Furthermore, annular seal accommodating portion 45 is filled with aliquid sealing agent for ensuring liquid tightness, when metal cover 12is assembled. Furthermore, the depth of the groove forming the annularseal accommodating portion 45 is determined by the length of annularreinforcing projecting portion 46 formed at the edge of exposure hole 42of metal cover 12 as described below.

FIGS. 11 and 12 show metal cover 12 according to the present embodiment.Metal cover 12 includes a lateral peripheral part 43 and a bottom part44, wherein bottom part 44 is formed by bending from one end of lateralperipheral part 43, and wherein bottom part 44 is formed with exposurehole 42 through which external terminal forming parts 13A, 13B, and 13Cof connector assembly 13 are exposed to the outside. Furthermore,opening end 37 is formed on the side opposite to bottom part 44, and isengaged with the end face part 15 of motor housing 11.

In a region of metal cover 12 close to the open end 37, three swagingrecesses 48 are formed. By pressing the swaging tool onto the swagingrecess 48, the wall of metal cover 12 is plastically deformed and fixedby swaging to swaging fixation portion 38 shown in FIG. 10.

Exposure hole 42 is formed near the center of bottom part 44 forexposing the external terminal forming parts 13A, 13B, and 13C ofconnector assembly 13 to the outside. Furthermore, at the peripheraledge of exposure hole 42 (in other words, at the inner periphery ofbottom part 44 forming the exposure hole 42), annular reinforcingprojecting portion 46 is formed by bending toward the inside of metalcover 12. Annular reinforcing projecting portion 46 may be formed bydrawing the metal cover 12.

Annular reinforcing projecting portion 46 has a shape extending in theaxial direction of rotating shaft 23 with metal cover 12 mounted to endface part 15, so that annular reinforcing projecting portion 46corresponds in position to the groove of annular seal accommodatingportion 45. Namely, annular reinforcing projecting portion 46 issubstantially parallel to the side walls forming the groove of annularseal accommodating portion 45.

The axial length of annular reinforcing projecting portion 46 isdetermined such that annular reinforcing projecting portion 46 is out ofintimate contact with the bottom face of the groove forming the annularseal accommodating portion 45. This ensures a margin for axialdimensional control of annular reinforcing projecting portion 46 andannular seal accommodating portion 45, and further allows a liquidsealing agent to be interposed between annular reinforcing projectingportion 46 and the inner wall surfaces of annular seal accommodatingportion 45, ensuring a function of liquid tightness.

FIG. 13 shows a cross-sectional view of metal cover 12 when metal cover12 is fixed by swaging to the end face part 15 of motor housing 11.

Before swaging and fixing the metal cover 12 to the end face part 15 ofmotor housing 11, the inside of annular seal accommodating portion 45formed in connector assembly 13 is filled with liquid sealing agent 49.Then, when metal cover 12 is assembled so as to cover the electroniccontrol section 9, annular reinforcing projecting portion 46 formed inbottom part 44 of metal cover 12 is inserted and accommodated in annularseal accommodating portion 45 formed in the connector assembly 13.

In this state, by pressing the swaging tool onto the swaging recess 48of metal cover 12, the wall of metal cover 12 is plastically deformedand fixed by swaging to swaging fixation portion 38 (see FIG. 10).During this operation, an external force due to swaging may act on metalcover 12 to deform exposure hole 42 and its vicinity of metal cover 12.However, in the present embodiment, the formation of annular reinforcingprojecting portion 46 serves to enhance the mechanical strength ofexposure hole 42 and its vicinity, and suppress deformation of exposurehole 42 and its vicinity and deformation of metal cover 12.

As shown in FIG. 13, annular reinforcing projecting portion 46 isaccommodated in annular seal accommodating portion 45 with apredetermined gap to each inner wall surface of annular sealaccommodating portion 45, wherein the gap is filled with liquid sealingagent 49. This ensures sufficient liquid tightness in this place. Theouter surface of liquid sealing agent 49 filled inside the annularreinforcing projecting portion 46 exceeds the surface of bottom part 44of metal cover 12 by a thickness (t).

Accordingly, no dent is formed between liquid sealing agent 49 and thewall surface of annular reinforcing projecting portion 46 housed inannular seal accommodating portion 45, allowing moisture to flow fromthe outside toward the bottom part 44, and thereby suppress corrosion ofannular reinforcing projecting portion 46. If it is exposed to saltwater or the like in particular, it promotes corrosion. However, thisconfiguration serves to suppress such corrosion.

The further configuration that annular reinforcing projecting portion 46is formed at the peripheral edge of exposure hole 42 formed in bottompart 44 of metal cover 12, serves to increase the mechanical strength ofthe periphery of exposure hole 42. Accordingly, even if an externalforce is applied to metal cover 12 in the process of assembling themetal cover or in the process of actual use, it is possible to suppressdeformation of the vicinity of the peripheral edge of exposure hole 42and deformation of metal cover 12.

For example, as described above, when metal cover 12 is fixed by swagingto the end face part 15 of motor housing 11, the swaging operation maycause an external force to act on exposure hole 42 of metal cover 12 soas to deform the peripheral region of exposure hole 42. However, theformation of annular reinforcing projecting portion 46 serves tosuppress deformation of the peripheral region of exposure hole 42.

In this way, the feature that annular reinforcing projecting portion 46is formed at the edge of exposure hole 42 formed in bottom part 44 ofmetal cover 12, and accommodated in annular seal accommodating portion45 formed around external terminal forming parts 13A, 13B, 13C ofconnector assembly 13, serves to enhance the mechanical strength of thesurrounding region of exposure hole 42, and thereby suppress deformationof metal cover 12.

In the present embodiment, annular reinforcing projecting portion 46 isformed by drawing the metal cover 12, but annular reinforcing projectingportion 46 may be provided by preparing a separate reinforcingprojecting portion, and fixing it to bottom part 44 of metal cover 12 bywelding, forging, etc. Furthermore, although annular reinforcingprojecting portion 46 is formed simultaneously with formation ofexposure hole 42, it is also possible to form an annular reinforcingprojecting portion, which has a shape corresponding to annular sealaccommodating portion 45, in the peripheral region around exposure hole42.

Liquid sealing agents 41 and 49 for liquid tightness, which are filledrespectively between metal cover 12 and end face part 15 and betweenmetal cover 12 and connector assembly 13, are implemented by an adhesivesynthetic resin. In the present embodiment, liquid sealing agents 41 and49 are implemented by a silicone-rubber-based elastic adhesive that iscured at room temperature or is cured by heating. Thissilicone-rubber-based elastic adhesive has a property of absorbingstress such as external vibration and impact, and is less subject tostress concentration on the adhesive interface. When an electric powersteering device is subject to vibration, impact, etc., peeling may occurat the adhesive interface and the function of liquid tightness may belost. However, the use of a silicone-rubber-based elastic adhesiveserves to reduce the risk of loss of the function of liquid tightness.

Furthermore, in the present embodiment, the feature that the sealing isimplemented by adhesive liquid sealing agents 41 and 49 allows the useof a liquid-tightening O-ring to be omitted. Liquid sealing agents 41and 49 may be implemented by a liquid gasket (FIPG: Formed In PlaceGasket) having an adhesive function, and may be implemented by amaterial that can be cured at room temperature or by heating.

By this configuration, it is possible to prevent moisture from enteringthe inside through the vicinity of abutment between annular reinforcingprojecting portion 46 at exposure hole 42 formed in bottom part 44 ofmetal cover 12 and annular seal accommodating portion 45 of connectorassembly 13. Also, it is possible to prevent moisture from entering theinside through the vicinity of the place of engagement between open end37 of metal cover 12 and step portion 35 of end face part 15 of motorhousing 11.

As described above, the present invention is characterized by including:a motor housing structured to house an electric motor, wherein the motorhousing includes an end face part opposite to an output part of arotating shaft of the electric motor, and wherein the electric motor isstructured to drive a controlled object of a mechanical system; anelectronic control part arranged at the end face part of the motorhousing; a connector assembly arranged on a side of the electroniccontrol part opposite to a side of the electronic control part thatfaces the end face part of the motor housing; and a metal coverstructured to cover the electronic control part from outside, whereinthe metal cover includes: a bottom part including: an exposure holethrough which an external terminal forming part is exposed to outside;and an annular reinforcing projecting portion formed at an edge of theexposure hole, and accommodated in an annular seal accommodatingportion; and a lateral peripheral part angled from the bottom part, andforming an opening through which the lateral peripheral part is fixed tothe end face part of the motor housing.

According to the foregoing, the feature that the annular reinforcingprojecting portion is formed at the edge of the exposure hole formed inthe bottom part of the metal cover, serves to enhance the mechanicalstrength of the surrounding region of the exposure hole, and therebysuppress the deformation of the metal cover.

The present invention is not limited to the embodiment described above,but includes various modified embodiments. The described embodiment isdetailed merely for easy understanding of the present invention, and thepresent invention is not limited to a form including all of the featuresdescribed above, for example. Part of features of one of the embodimentsmay be replaced with features of another one of the embodiments.Features of one of the embodiments may be additionally provided withfeatures of another one of the embodiments. Part of features of each ofthe embodiments may be additionally provided with other features orremoved or replaced.

The electric drive device according to the embodiment described abovemay be exemplified as follows.

According to one aspect, an electric drive device includes: a motorhousing structured to house an electric motor, wherein the motor housingincludes an end face part opposite to an output part of a rotating shaftof the electric motor, and wherein the electric motor is structured todrive a controlled object of a mechanical system; an electronic controlpart arranged at the end face part of the motor housing; a connectorassembly arranged on a side of the electronic control part opposite to aside of the electronic control part that faces the end face part of themotor housing; and a metal cover structured to cover the electroniccontrol part from outside, wherein the metal cover includes: a bottompart including: an exposure hole through which an external terminalforming part is exposed to outside; and an annular reinforcingprojecting portion formed at an edge of the exposure hole; and a lateralperipheral part angled from the bottom part, and forming an openingthrough which the lateral peripheral part is fixed to the end face partof the motor housing.

According to a preferable aspect, the electric drive device isconfigured such that the annular reinforcing projecting portion angledfrom a portion of the bottom part that defines the exposure hole.

According to another preferable aspect, the electric drive deviceaccording to one of the foregoing aspects is configured such that theannular reinforcing projecting portion is accommodated in an annularseal accommodating portion that is formed around the external terminalforming part and filled with a liquid sealing agent.

According to a further preferable aspect, the electric drive deviceaccording to one of the foregoing aspects is configured such that theend face part of the motor housing includes a swaging recess; and themetal cover includes a wall face pressed and swaged into the swagingrecess for fixation of the metal cover to the end face part of the motorhousing.

According to a further preferable aspect, the electric drive deviceaccording to one of the foregoing aspects is configured such that theannular seal accommodating portion is recess-shaped in a cross sectionalview taken along a plane in an axial direction of the rotating shaft;the annular reinforcing projecting portion is accommodated in theannular seal accommodating portion with a predetermined clearance to aninner wall surface of the annular seal accommodating portion; and theclearance is filled with the liquid sealing agent.

According to a further preferable aspect, the electric drive deviceaccording to one of the foregoing aspects is configured such that theliquid sealing agent located radially inside the annular reinforcingprojecting portion has an outer surface projecting beyond a surface ofthe bottom part of the metal cover.

According to a further preferable aspect, the electric drive deviceaccording to one of the foregoing aspects is configured such that aspace between the end face part of the motor housing and the opening ofthe metal cover is filled with the liquid sealing agent.

The electric power steering device according to the embodiment describedabove may be exemplified as follows.

According to one aspect, an electric power steering device includes: anelectric motor structured to apply a steering assist force to a steeringshaft, depending on an output from a torque sensor, wherein the torquesensor is structured to sense a direction of rotation of the steeringshaft and a rotating torque applied to the steering shaft; a motorhousing structured to house the electric motor, wherein the motorhousing includes an end face part opposite to an output part of arotating shaft of the electric motor; an electronic control partarranged at the end face part of the motor housing; a connector assemblyarranged on a side of the electronic control part opposite to a side ofthe electronic control part that faces the end face part of the motorhousing; and a metal cover structured to cover the electronic controlpart from outside, wherein the metal cover includes: a bottom partincluding: an exposure hole through which an external terminal formingpart is exposed to outside; and an annular reinforcing projectingportion formed at an edge of the exposure hole; and a lateral peripheralpart angled from the bottom part, and forming an opening through whichthe lateral peripheral part is fixed to the end face part of the motorhousing.

According to a preferable aspect, the electric power steering device isconfigured such that the annular reinforcing projecting portion angledfrom a portion of the bottom part that defines the exposure hole.

According to another preferable aspect, the electric power steeringdevice according to one of the foregoing aspects is configured such thatthe annular reinforcing projecting portion is accommodated in an annularseal accommodating portion that is formed around the external terminalforming part and filled with a liquid sealing agent.

According to a further preferable aspect, the electric power steeringdevice according to one of the foregoing aspects is configured such thatthe end face part of the motor housing includes a swaging recess; andthe metal cover includes a wall face pressed and swaged into the swagingrecess for fixation of the metal cover to the end face part of the motorhousing.

According to a further preferable aspect, the electric power steeringdevice according to one of the foregoing aspects is configured such thatthe annular seal accommodating portion is recess-shaped in a crosssectional view taken along a plane in an axial direction of the rotatingshaft; the annular reinforcing projecting portion is accommodated in theannular seal accommodating portion with a predetermined clearance to aninner wall surface of the annular seal accommodating portion; and theclearance is filled with the liquid sealing agent.

According to a further preferable aspect, the electric power steeringdevice according to one of the foregoing aspects is configured such thatthe liquid sealing agent located radially inside the annular reinforcingprojecting portion has an outer surface projecting beyond a surface ofthe bottom part of the metal cover.

According to a further preferable aspect, the electric power steeringdevice according to one of the foregoing aspects is configured such thata space between the end face part of the motor housing and the openingof the metal cover is filled with the liquid sealing agent.

1. An electric drive device comprising: a motor housing structured tohouse an electric motor, wherein the motor housing includes an end facepart opposite to an output part of a rotating shaft of the electricmotor, and wherein the electric motor is structured to drive acontrolled object of a mechanical system; an electronic control partarranged at the end face part of the motor housing; a connector assemblyarranged on a side of the electronic control part opposite to a side ofthe electronic control part that faces the end face part of the motorhousing; and a metal cover structured to cover the electronic controlpart from outside, wherein the metal cover includes: a bottom partincluding: an exposure hole through which an external terminal formingpart is exposed to outside; and an annular reinforcing projectingportion formed at an edge of the exposure hole; and a lateral peripheralpart angled from the bottom part, and forming an opening through whichthe lateral peripheral part is fixed to the end face part of the motorhousing.
 2. The electric drive device as claimed in claim 1, wherein theannular reinforcing projecting portion is angled from a portion of thebottom part that defines the exposure hole.
 3. The electric drive deviceas claimed in claim 2, wherein the annular reinforcing projectingportion is accommodated in an annular seal accommodating portion that isformed around the external terminal forming part and filled with aliquid sealing agent.
 4. The electric drive device as claimed in claim3, wherein: the end face part of the motor housing includes a swagingrecess; and the metal cover includes a wall face pressed and swaged intothe swaging recess for fixation of the metal cover to the end face partof the motor housing.
 5. The electric drive device as claimed in claim4, wherein: the annular seal accommodating portion is recess-shaped in across sectional view taken along a plane in an axial direction of therotating shaft; the annular reinforcing projecting portion isaccommodated in the annular seal accommodating portion with apredetermined clearance to an inner wall surface of the annular sealaccommodating portion; and the clearance is filled with the liquidsealing agent.
 6. The electric drive device as claimed in claim 5,wherein the liquid sealing agent located radially inside the annularreinforcing projecting portion has an outer surface projecting beyond asurface of the bottom part of the metal cover.
 7. The electric drivedevice as claimed in claim 3, wherein a space between the end face partof the motor housing and the opening of the metal cover is filled withthe liquid sealing agent.
 8. An electric power steering devicecomprising: an electric motor structured to apply a steering assistforce to a steering shaft, depending on an output from a torque sensor,wherein the torque sensor is structured to sense a direction of rotationof the steering shaft and a rotating torque applied to the steeringshaft; a motor housing structured to house the electric motor, whereinthe motor housing includes an end face part opposite to an output partof a rotating shaft of the electric motor; an electronic control partarranged at the end face part of the motor housing; a connector assemblyarranged on a side of the electronic control part opposite to a side ofthe electronic control part that faces the end face part of the motorhousing; and a metal cover structured to cover the electronic controlpart from outside, wherein the metal cover includes: a bottom partincluding: an exposure hole through which an external terminal formingpart is exposed to outside; and an annular reinforcing projectingportion formed at an edge of the exposure hole; and a lateral peripheralpart angled from the bottom part, and forming an opening through whichthe lateral peripheral part is fixed to the end face part of the motorhousing.
 9. The electric power steering device as claimed in claim 8,wherein the annular reinforcing projecting portion is angled from aportion of the bottom part that defines the exposure hole.
 10. Theelectric power steering device as claimed in claim 9, wherein theannular reinforcing projecting portion is accommodated in an annularseal accommodating portion that is formed around the external terminalforming part and filled with a liquid sealing agent.
 11. The electricpower steering device as claimed in claim 10, wherein: the end face partof the motor housing includes a swaging recess; and the metal coverincludes a wall face pressed and swaged into the swaging recess forfixation of the metal cover to the end face part of the motor housing.12. The electric power steering device as claimed in claim 11, wherein:the annular seal accommodating portion is recess-shaped in a crosssectional view taken along a plane in an axial direction of the rotatingshaft; the annular reinforcing projecting portion is accommodated in theannular seal accommodating portion with a predetermined clearance to aninner wall surface of the annular seal accommodating portion; and theclearance is filled with the liquid sealing agent.
 13. The electricpower steering device as claimed in claim 12, wherein the liquid sealingagent located radially inside the annular reinforcing projecting portionhas an outer surface projecting beyond a surface of the bottom part ofthe metal cover.
 14. The electric power steering device as claimed inclaim 10, wherein a space between the end face part of the motor housingand the opening of the metal cover is filled with the liquid sealingagent.